Method and apparatus for reporting inter-frequency measurement using RACH message in a mobile communication system

ABSTRACT

A user equipment (UE) is provided which reduces uplink signaling overhead in the process of reporting inter-frequency measurement results over a RACH. For measurement reporting, the UE receives an SIB including a cell information list for non-used frequency cells and a threshold from an RNC, compares signal strengths of signals received from the non-used frequency cells with the threshold, and acquires at least one inter-frequency cell ID indicating at least one non-used frequency cell having signal strength exceeding the threshold from the cell information list. The at least one inter-frequency cell ID is included in a RACH message as measurement result information for the at least one non-used frequency cell, and transmitted to the RNC. The RNC determines that the cell corresponding to the inter-frequency cell ID has signal strength exceeding the threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.11/417,213, filed May 4, 2006, now U.S. Pat. No. 8,270,365, entitled“Method and Apparatus for Reporting Inter-Frequency Measurement UsingRACH Message in a Mobile Communication System”, the entire contents ofwhich are hereby incorporated by reference, which claims the benefitunder 35 U.S.C. §119(a) of Korean Patent Application No. 10-2005-0037773entitled “Method and Apparatus for Reporting Inter-Frequency MeasurementUsing RACH Message in a Mobile Communication System”, filed in theKorean Intellectual Property Office on May 4, 2005, Korean PatentApplication No. 10-2005-0038640 entitled “Method and Apparatus forReporting Inter-Frequency Measurement Using RACH Message in a MobileCommunication System”, filed in the Korean Intellectual Property Officeon May 9, 2005, and Korean Patent Application No. 10-2005-0104634entitled “Method and Apparatus for Reporting Inter-Frequency MeasurementUsing RACH Message in a Mobile Communication System”, filed in theKorean Intellectual Property Office on Nov. 2, 2005, the entiredisclosures of all of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a mobile communication systememploying Code Division Multiple Access (CDMA). In particular, thepresent invention relates to a method and apparatus in which a terminal(or user equipment (UE)) reports measurement results to the system.

2. Description of the Related Art

A Universal Mobile Telecommunication Service (UMTS) system, which is anasynchronous 3^(rd) generation (3G) mobile communication systememploying Wideband Code Division Multiple Access (WCDMA) based onEuropean Global System for Mobile Communications (GSM) and GeneralPacket Radio Services (GPRS), provides consistent service that iscapable of allowing telephone or computer users to transmit packetswitched text, digitized voice, video, and multimedia data, at rates ofabout 2 Mbps all over the world. UMTS uses a virtual access technology,the so-called packet switched access based on a packet protocol such asInternet Protocol (IP), and can always access any other terminals in thenetwork.

In the 3^(rd) Generation Project Partnership (3GPP), the standard forthe asynchronous 3G mobile communication system, a Random Access Channel(RACH) which is an uplink common channel, is used for network access andcontrol and transmission of short-length data. Such logical channels,for example a Dedicated Control Channel (DCCH), a Common Control Channel(CCCH), and a Dedicated Traffic Channel (DTCH), can be mapped to theRACH which is a transport channel.

The RACH can be used for measurement reporting. That is, a UE includesmeasurement results indicating its measured radio strengths of othercells and other frequencies in a Radio Resource Control (RRC) messagefor signaling, transmitted to a Radio Network Controller (RNC) over theRACH. The measurement results are used by the system to determinewhether a communication environment of a UE is good, and whether the UEis located in a handover region. Measurement control system informationneeded for performing inter-frequency and intra-frequency measurementsis included in system information blocks (SIB) received from the RNC.The UE, in an idle mode or a connected mode, receives a SIB transmittedover a broadcast channel and acquires the measurement control systeminformation therefrom.

Table 1 and Table 2 below show, by way of example, a format of a RACHmessage for reporting inter-frequency measurement system information andinter-frequency measurement results, included in SIB11/12 to be used forreporting the inter-frequency measurement results. SIB11/12 includesmeasurement-related control information used in the current cell,wherein SIB11 is for an idle mode UE and SIB12 is for a connected modeUE. If there is no SIB12, the connected mode UE also refers to SIB11.

Table 1 consists of Table 1a to Table 1c. Table 1a shows a format of‘Inter-frequency measurement system information’ included in SIB11/12.In Table 1a, an ‘Inter-frequency reporting quantity for RACH reporting’information element (IE) and a ‘maximum number of inter-frequencyreported cells on RACH’ IE are information for including inter-frequencymeasurement result values in the RACH message.

TABLE 1a Inter-frequency measurement system information in SIB 11/12Information Semantics Element/Group name Multi Type and referencedescription Inter-frequency cell info list Inter-frequency cell infolist Inter-frequency reporting Inter-frequency quantity for RACHreporting quantity for Reporting RACH Reporting Maximum number of inter-Maximum number frequency of reported cells Reported cells on RACH onRACH

TABLE 1b Inter-frequency reporting quantity for RACH reportingInformation Element/ Semantics Group name Multi Type and referencedescription CHOICE mode >FDD >>Reporting quantity Enumerated(CPICHEc/N0, CPICH RSCP, No report) >TDD >>Reporting quantity 1 to 2list >>>Reporting quantity Enumerated(Timeslot ISCP, Primary CCPCH RSCP,No report)

TABLE 1c Maximum number of inter-frequency reported cells on RACH TypeSemantics Information Element/Group name Multi and reference descriptionMaximum number of reported cells Integer(1 . . . 8) per for all reportednon-used frequencies

A ‘Reporting quantity’ IE as shown in Table 1b indicates which reportingquantity is to be used when the inter-frequency measurement systeminformation is transmitted over the RACH. For example, in a cell usingFrequency Division Duplex (FDD), a chip-to-noise energy Ec/No of aCommon Pilot Channel (CPICH) or a Receive Signal Code Power (RSCP) ofthe CPICH is used as a measurement result, or ‘No report’ can be used totransmit no inter-frequency measurement result. A ‘Maximum number’ IE asshown in Table 1c indicates the maximum number of cells to which theinter-frequency measurement results will be transmitted over the RACH.

In transmitting the RACH message including the inter-frequencymeasurement results, if the ‘Reporting quantity’ IE and the ‘Maximumnumber’ IE are included in SIB11/12, the UE writes and includes as muchinter-frequency measurement results as the ‘Maximum number’ IE in theRACH message according to the ‘Reporting quantity’ IE.

For example, if the ‘Maximum number’ IE is set to ‘2’ and the ‘Reportingquantity’ IE indicates an Ec/No of the CPICH, the UE includes aninter-frequency cell info list for 2 non-used frequency band cells andCPICH Ec/No for the non-used frequency band cells in the RACH messageaccording to the measurement results for the non-used frequency bandcells whose frequencies are different from the currently used frequency.Table 2 below shows an information format of the inter-frequencymeasurement results included in the RACH message.

TABLE 2 Measured results on RACH Information Element/ Type and Semanticsgroup name Multi reference description Measurement result for currentcell Measurement results for 1 to monitored cells on non-used <maxFreq>frequencies >Frequency info Frequency >Inter-frequency cell infomeasurement results >>CHOICE mode >>>FDD >>>>Primary CPICH info PrimaryCPICH info >>>>CHOICE measurement One spare quantity value isneeded. >>>>>CPICH Ec/N0 Integer(0 . . . 49) In dB. According toCPICH_Ec/ No in [19]. Fourteen spare values are needed. >>>>>CPICH RSCPInteger(0 . . . 91) In dBm. According to CPICH_ RSCP_LEV in [19].Thirty-six spare values are needed. >>>TDD >>>>Cell parameters Id Cellparameters Id >>>>Primary CCPCH RSCP Primary CCPCH RSCP info

In this case, monitored cells consist of neighbouring cells.

Condition Explanation DCCH This IE is optionally present when DCCH isused and not needed otherwise.

As shown in Table 2, in reporting the inter-frequency measurementresults over the RACH message, the UE includes as much ‘Frequency Info’,‘Primary CPICH info’ and ‘measurement quantity’ as the ‘Maximum number’IE, transmitted through SIB11/12, in the RACH message, causing anexcessive increase in the size of the RACH message.

In addition, the UE includes the measurement results for the non-usedfrequencies in the RACH message even though the channels states of thenon-used frequencies are bad. As is known to those skilled in the art,in order to transmit a message over the RACH, the UE should first send arequest for RACH transmission approval to a base station (or Node B) andreceive response information indicating approval of the RACHtransmission from the Node B. Therefore, when RACH transmission approvalrequests are issued by a plurality of UEs, each UE may fail to obtainRACH transmission approval within the ‘Maximum number’. Nonetheless, ifeach UE unnecessarily transmits the measurement results on severalnon-used frequencies over the RACH, signaling overhead of the RACH mayincrease excessively.

That is, in conventional measurement reporting, the measurement resultinformation included in the RACH message includes many IEs, and there isno criterion for reporting, by the UE, the measurement results over theRACH, causing an increase in an uplink load.

Accordingly, a need exists for a system and method for effectively andefficiently reporting measurement results.

SUMMARY OF THE INVENTION

An object of embodiments of the present invention is to substantiallysolve at least the above problems and/or disadvantages, and to provideat least the advantages below. Accordingly, embodiments of the presentinvention provide a method and apparatus in which a UE minimizes aninformation format of measurement reports transmitted over a RACH tothereby reduce signaling overhead of the RACH message.

According to one aspect of embodiments of the present invention, amethod is provided for reporting an inter-frequency measurement resultusing a random access channel (RACH) message in a mobile communicationsystem. The method comprises the steps of receiving a system informationblock (SIB) comprising an inter-frequency cell information list fornon-used frequency cells and a threshold from the system forinter-frequency measurement reporting, measuring signal strengths ofsignals received from the non-used frequency cells and comparing themeasured signal strengths with the threshold and if there is any signalstrength exceeding the threshold, acquiring at least one inter-frequencycell identifier (ID) indicating at least one non-used frequency cellhaving the signal strength exceeding the threshold from theinter-frequency cell information list, and including the at least oneinter-frequency cell ID in the RACH message as inter-frequencymeasurement result information and transmitting the RACH message to thesystem.

According to another aspect of embodiments of the present invention, auser equipment (UE) apparatus is provided for reporting aninter-frequency measurement result using a random access channel (RACH)message in a mobile communication system. The apparatus comprises asystem information block (SIB) reception and analysis unit for receivinga SIB comprising an inter-frequency cell information list for non-usedfrequency cells and a threshold from the system for inter-frequencymeasurement reporting, a measurement unit for measuring signal strengthsof signals received from the non-used frequency cells, a measurementreport decision unit for comparing the measured signal strengths withthe threshold and if there is at least one signal strength exceeding thethreshold, determining to perform inter-frequency measurement reporting,and a measurement report unit for, if the measurement report decisionunit determines to perforin inter-frequency measurement reporting,acquiring at least one inter-frequency cell identifier (ID) indicatingat least one non-used frequency cell having the signal strengthexceeding the threshold from the inter-frequency cell information list,including the at least one inter-frequency cell ID in the RACH messageas inter-frequency measurement result information, and transmitting theRACH message to the system.

According to another aspect of embodiments of the present invention, amethod is provided for receiving inter-frequency measurement reportingusing a random access channel (RACH) message in a mobile communicationsystem. The method comprises the steps of transmitting a systeminformation block (SIB) comprising an inter-frequency cell informationlist for non-used frequency cells and a threshold to each of controlledcells to control inter-frequency measurement reporting, receiving a RACHmessage from a user equipment (UE) located in one of the controlledcells, extracting at least one inter-frequency cell identifier (ID)corresponding to inter-frequency measurement result information from theRACH message, acquiring cell information corresponding to the extractedinter-frequency cell ID referring to the inter-frequency cellinformation list, and acquiring a measurement result indicating signalstrength corresponding to the inter-frequency cell ID referring to atleast one of the inter-frequency measurement result information and thethreshold.

According to yet another aspect of embodiments of the present invention,a radio network controller (RNC) is provided for receivinginter-frequency measurement reporting using a random access channel(RACH) message in a mobile communication system. The RNC comprises asystem information system (SIB) generation and transmission unit fortransmitting an SIB comprising an inter-frequency cell information listfor non-used frequency cells and a threshold to each of controlled cellsto control inter-frequency measurement reporting, a RACH receiver forreceiving a RACH message from a user equipment (UE) located in one ofthe controlled cells and extracting at least one inter-frequency cellidentifier (ID) corresponding to inter-frequency measurement resultinformation from the RACH message, a cell index mapping unit foracquiring cell information corresponding to the extractedinter-frequency cell ID referring to the inter-frequency cellinformation list, and a measurement result analyzer for acquiring ameasurement result indicating signal strength corresponding to theinter-frequency cell ID referring to at least one of the inter-frequencymeasurement result information and the threshold.

According to still another aspect of embodiments of the presentinvention, a method is provided for reporting an inter-frequencymeasurement result using a random access channel (RACH) message in amobile communication system. The method comprises the steps ofreceiving, by a control radio network controller (CRNC) that controls acurrent cell where a user equipment (UE) is located, a RACH messagecomprising at least one inter-frequency cell identifier (ID) for atleast one non-used frequency cell as inter-frequency measurement resultinformation from the UE, acquiring at least one cell informationcorresponding to the at least one inter-frequency cell ID, andtransmitting an uplink signaling transfer message comprising aninter-frequency cell information list having the acquired at least onecell information, and the RACH message, to a serving radio networkcontroller (SRNC) that controls radio resources of the UE.

According to still another aspect of embodiments of the presentinvention, a method is provided for receiving inter-frequencymeasurement reporting using a random access channel (RACH) message in amobile communication system. The method comprises the steps ofreceiving, by a serving radio network controller (SRNC) that controlsradio resources of a user equipment (UE), an uplink signaling transfermessage comprising a RACH message having at least one inter-frequencycell identifier (ID) for at least one non-used frequency cell, and atleast one cell information corresponding to the at least oneinter-frequency cell ID as inter-frequency measurement resultinformation, from a control radio network controller (CRNC) thatcontrols a current cell where the UE is located, and determining radioquality of the UE depending on the inter-frequency measurement resultinformation and the at least one cell information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of embodiments ofthe present invention will become more apparent from the followingdetailed description when taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram schematically illustrating exemplary architecture ofa general UMTS mobile communication system;

FIG. 2 is a diagram illustrating an exemplary operation of transmittinginter-frequency measurement results over a RACH according to anembodiment of the present invention;

FIGS. 3A and 3B are flowcharts illustrating an exemplary UE operation oftransmitting a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention;

FIG. 4 is a flowchart illustrating an exemplary RNC operation ofreceiving a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention;

FIG. 5 is a diagram illustrating an exemplary UE structure fortransmitting a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention;

FIG. 6 is a diagram illustrating an exemplary RNC structure forreceiving a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention;

FIG. 7 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a first embodiment of thepresent invention;

FIG. 8 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a second embodiment of thepresent invention;

FIG. 9 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a third embodiment of thepresent invention;

FIG. 10 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a fourth embodiment of thepresent invention;

FIGS. 11A and 11B are flowcharts illustrating an exemplary operation ofa CRNC according to the fourth embodiment of the present invention; and

FIG. 12 is a flowchart illustrating an exemplary operation of an SRNCaccording to the fourth embodiment of the present invention.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Several exemplary embodiments of the present invention will now bedescribed in detail with reference to the annexed drawings. In thefollowing description, a detailed description of known functions andconfigurations incorporated herein has been omitted for clarity andconciseness.

Although exemplary embodiments of the present invention will bedescribed with reference to a UMTS mobile communication system proposedin 3GPP, the standard for the asynchronous 3G mobile communicationsystem, embodiments of the present invention can also be applied to allkinds of mobile communication systems employing the measurement report.

FIG. 1 is a diagram schematically illustrating exemplary architecture ofa general UMTS mobile-communication system.

Referring to FIG. 1, a UMTS system comprises a Core Network (CN) 100 anda plurality of Radio Network Subsystems (RNSs) 110 and 120. The RNSs 110and 120 comprise a UMTS Terrestrial Radio Access Network (UTRAN). The CN100 is comprised of a Serving GPRS Support Node (SGSN) and a GatewayGPRS Support Node (GGSN) to connect the UTRAN to a packet data networksuch as the Internet.

The RNSs 110 and 120 each comprise Radio Network Controllers (RNCs) 111and 112, and a plurality of Node Bs 115, 113, 114 and 116. Specifically,the RNS 110 is comprised of the RNC 111 and the Node Bs 115 and 113,while the RNS 120 is comprised of the RNC 112 and the Node Bs 114 and116. The RNCs 111 and 112 are classified as either a serving RNC, adrift RNC, and a control RNC, according to a role of their userequipments (UEs). The serving RNC manages information on a UE 130 andtakes charge of data exchange with the CN 100, and the drift RNCdirectly wirelessly connects with the UE 130. The control RNC controlsradio resources of each of the Node Bs.

The RNCs 111 and 112 are connected to the Node Bs 115, 113, 114 and 116,via interfaces called ‘Iub’, and the connection between the RNCs 111 and112 is made by an interface called ‘Iur’. Although not illustrated inFIG. 1, the connection between the UE 130 and the UTRAN is made by a Uuinterface. The RNCs 111 and 112 allocate radio resources for the Node Bs115, 113, 114 and 116 managed by themselves, and the Node Bs 115, 113,114 and 116 provide the radio resources allocated from the RNCs 111 and112 to the UE 130. The radio resources are configured cell by cell, andthe radio resources provided by each Node B are radio resourcesassociated with a specific cell managed by the corresponding Node B.

The UE 130 sets up a radio channel using radio resources associated witha specific cell managed by any one of the Node Bs 115, 113, 114 and 116,and exchanges data over the set radio channel. The UE 130 identifiesphysical channels generated per cell, and measures signal qualities ofdetectable physical channels of other cells except for the cell to whichit is currently tuned. The measurement results reported from the UE 130to the RNCs 111 and 112 comprise intra-frequency measurement results forthe frequency channel to which the UE 130 is currently tuned, andinter-frequency measurement result for non-used frequency channels.

According to exemplary embodiments of the present invention, intransmitting a RACH message comprising the measurement results, the UEpreviously sets a particular threshold for inter-frequency measurementreporting on the RACH message, and reports a correspondinginter-frequency measurement result value through the RACH message onlyfor the cells of the non-used frequency bands having signal qualityhigher than the preset threshold. Herein, the “non-used frequency bands”refer to the frequency bands unused by the UE, and the “cells of thenon-used frequency bands” refer to the cells servicing the unusedfrequency bands.

If there is no cell of the non-used frequency band having the signalquality higher than the threshold, the UE does not include theinter-frequency measurement result information in the RACH message. Inaddition, for example, even though the ‘Maximum number’ is ‘4’, if thereis only one cell of the non-used frequency band having the signalquality higher than the preset threshold, the UE reports only themeasurement result on the one non-used frequency band cell through theRACH message.

When reporting the measurement results on the cells of the non-usedfrequency bands having the signal quality higher than the threshold, theUE uses a short index referable to SIB11/12 for the cells of thenon-used frequency bands, instead of using frequency information andprimary CPICH information. That is, the UE transmits cell identificationinformation and the measurement results or transmits only cellidentification information, instead of transmitting the frequencyinformation, primary CPICH information, and measurement results. The RNCacquires frequency information and primary CPICH information of the cellindicated by the cell identification information, by referring to theSIB11/12. If the UE transmits only the cell identification informationwithout the measurement results, the RNC determines that the cell of thereceived cell identification information has at least the signal qualityhigher than the threshold.

FIG. 2 is a diagram illustrating an exemplary operation of transmittinginter-frequency measurement results over a RACH according to anembodiment of the present invention.

As illustrated in FIG. 2, in step 202, an RNC transmits inter-frequencyRACH reporting quantity and maximum number of inter-frequency reportedcells as inter-frequency RACH reporting information, which isinter-frequency measurement information, through SIB11/12. Theinter-frequency RACH reporting quantity is a kind of information to beused for reporting the inter-frequency measurement results through aRACH message, and can indicate CPICH Ec/No or CPICH RSCP. The maximumnumber of inter-frequency reported cells indicates the maximum number ofcells to which the inter-frequency measurement results will betransmitted through the RACH message. Additionally, the inter-frequencymeasurement control information comprises an inter-frequency RACHreporting threshold.

In step 204, a UE compares the measurement results measured for thecells of the non-used frequency bands with the threshold. In step 206,the UE transmits a RACH message comprising only the inter-frequencymeasurement result information for the cells of the non-used frequencybands having signal quality higher than the threshold to the RNC.

The UE applies the maximum number only for the cells of the non-usedfrequency bands having radio strength higher than a predeterminedthreshold. For example, for the maximum number=4, if the number of thenon-used frequency cells whose inter-frequency measurement results aregreater than the threshold is 2, the UE includes measurement resultinformation for the 2 cells in the RACH message. If there is no cell ofthe non-used frequency having the measurement result greater than thethreshold, the UE transmits no inter-frequency measurement resultinformation through the RACH message. However, if the number of thenon-used frequency cells having the measurement results greater than thethreshold exceeds 4, the UE transmits measurement result information for4 non-used frequency cells having the best radio strength through theRACH message. The measurement result information comprises cellidentification information for the non-used frequency cells whose radiostrength exceeds the threshold, and optionally comprises measurementresults (i.e., Ec/No or RSCP of CPICH) of the non-used frequency cells.

The RACH message comprises a short index referenced to SIB11/12 as cellidentification information. That is, the UE indicates the non-usedfrequency cells, using short cell indexes indicating the order of thenon-used frequency cells included in an inter-frequency cell info listin SIB11/12. In the following description, the short cell index will bereferred to as an ‘inter-frequency cell ID’. The inter-frequency cellinfo list transmitted on SIB11/12 comprises cell information for 1 ˜maxCellMeas non-used frequency cells. In this case, short indexes of thenon-used frequency cells are set to ‘0’ to ‘maxCellMeas-1’, and theshort indexes are used as inter-frequency cell IDs for the non-usedfrequency cells. In example, maxCellMeas is set to 32, so theinter-frequency cell ID has least 5 bits.

The RNC, upon receiving the RACH message, acquires frequency informationand primary CPICH information for a corresponding cell, referring to theorder of the cells included in the inter-frequency cell info list in theSIB11/12. This is possible because the RNC is already aware of thefrequency information and primary CPICH information for all cellsmanaged by itself. In addition, the RNC can be aware that even though nointer-frequency measurement result is included in the RACH message, atleast the cells whose cell identification information is included in theRACH message have radio strength exceeding the threshold. For example,if the non-used frequency cells having radio strength exceeding thethreshold are listed in the first, fifth and twelfth points of theinter-frequency cell info list, inter-frequency cell IDs of the non-usedfrequency cells are 0, 4 and 11, respectively. As another example, theRACH message may explicitly comprise measurement result values measuredby the EU in addition to the cell identification information.

Tables 3 and 4 below show, by way of example, formats of inter-frequencymeasurement system information included in SIB11/12 to be used forreporting inter-frequency measurement results and inter-frequencymeasurement information included in the RACH message for inter-frequencymeasurement reporting according to an embodiment of the presentinvention. SIB11/12 comprises measurement control information used inthe cell, wherein SIB11 is for an idle mode UE and SIB12 is for aconnected mode UE. If there is no SIB12, the connected mode UE alsorefers to SIB11.

Table 3 consists of Table 3a and Table 3b. Table 3a shows a format ofinter-frequency measurement system information included in SIB11/12, andTable 3b shows a format of inter-frequency RACH reporting informationincluded in the inter-frequency measurement system information.

TABLE 3a Inter-frequency measurement system information in SIB 11/12Information Element/ Semantics Group name Multi Type and referencedescription Inter-frequency cell info list Inter-frequency cell infolist Inter-frequency RACH Inter-frequency reporting information RACHreporting information Maximum number of inter- Maximum number offrequency reported cells on Reported cells on RACH RACH

TABLE 3b Inter-frequency RACH reporting information Information Element/Type and Semantics Group name Multi reference description CHOICEmode >FDD >> Inter-frequency Enumerated(CPICH RACH reporting Ec/N0,CPICH quantity RSCP) >TDD >>Reporting 1 to 2 quantity list >>>Inter-frequency Enumerated(Timeslot RACH reporting ISCP, Primaryquantity CCPCH RSCP) Inter-frequency Integer(−115 . . . 0) Ranges useddepend RACH on measurement reporting threshold quantity. CPICH Ec/ No−24 . . . 0 dB CPICH/ Primary CCPCH RSCP −115 . . . −25dBm. Maximumnumber Integer(1 . . . 8) Indicates the total of inter-frequency numberfor all reported cells non-used frequencies

In Table 3a, the inter-frequency cell info list comprisesinter-frequency cell ID, frequency information, and primary CPICHinformation. In addition, inter-frequency RACH reporting information iscontrol information referred to when inter-frequency measurement resultsare included in the RACH message. The inter-frequency RACH reportinginformation, as shown in Table 3b, comprises inter-frequency RACHreporting quantity, inter-frequency RACH reporting threshold, andmaximum number of inter-frequency reported cells. The inter-frequencyRACH reporting quantity and the maximum number of inter-frequencyreported cells have been described above. That is, the inter-frequencyRACH reporting quantity indicates a kind of the inter-frequencymeasurement results reported over the RACH, and the maximum number ofinter-frequency reported cells indicates the maximum number of cells towhich the inter-frequency measurement results will be transmitted overthe RACH.

The threshold indicates a reference value used by the UE to includeinter-frequency measurement information over the RACH. That is, the UEincludes the inter-frequency measurement results in the RACH messageonly for the cells of the non-used frequencies having radio strengthhigher than the threshold. If there is no cell of the non-used frequencyhaving radio strength higher than the threshold, the UE reducessignaling overhead because there is no need to include theinter-frequency measurement results in the RACH message. Therefore, themeasurement results included in the RACH message are always greater thanthe threshold.

Table 4 below shows an information format of inter-frequency measurementresults included in an RRC message transmitted by the UE over the RACHaccording to an embodiment of the present invention.

TABLE 4 Measured results on RACH Information Element/ Type and Semanticsgroup name Multi reference description Measurement result for currentcell Measurement results 1 to for monitored cells on <maxFreq> non-usedfrequencies >Inter-frequency cell Integer(0 . . . id <maxCellMeas>−1)

In this case, monitored cells consist of neighbouring cells.

Condition Explanation DCCH This IE is optionally present when DCCH isused and not needed otherwise.

Although it is shown in Table 4 that inter-frequency cell IDs referredto the order of a given inter-frequency cell info list are used forinter-frequency measurements of SIB11/12, the original unique cell IDsfor identifying the whole cells in the mobile communication system mayalso be used in another embodiment of the present invention. Further, inembodiments of the present invention, the RACH message can furthercomprise only one of the inter-frequency cell ID and the cell ID, orcomprise the corresponding measurement result along with any one of theinter-frequency cell ID and the cell ID.

FIGS. 3A and 3B are flowcharts illustrating an exemplary UE operation oftransmitting a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention.

As illustrated in FIGS. 3A and 3B, in step 302, a UE determines totransmit a RACH message optionally comprising inter-frequencymeasurement reporting over a RACH. In step 304, the UE checks whetherinter-frequency RACH reporting information is included in a SIB12received from the system. If there is no inter-frequency RACH reportinginformation included in the SIB12, the UE checks in step 308 whetherinter-frequency RACH reporting information is included in a SIB11 beingbroadcast in the current cell. If the SIB12 is not being broadcast inthe current cell and if there is no inter-frequency RACH reportinginformation included in the SIB11, the UE includes no inter-frequencymeasurement result information in the in the RACH message in step 310.

If the inter-frequency RACH reporting information is included in theSIB12 in step 304, or if the inter-frequency RACH reporting informationis included in step SIB11 in step 308, the UE checks in step 312 whetherto include inter-frequency measurement reporting in the RACH message. Ifthe inter-frequency measurement reporting is unavailable, the UE canperform error handling or transmit a RACH message with nointer-frequency measurement reporting in step 314.

However, if the inter-frequency measurements are available, the UEchecks in step 316 whether there is any non-used frequency cell havingradio strength higher than the inter-frequency RACH reporting thresholdincluded in the inter-frequency RACH reporting information. If there isno non-used frequency cell having radio strength higher than thethreshold, the UE includes no inter-frequency measurement result in theRACH message in step 318. However, if there are cells of the non-usedfrequencies having radio strength higher than the threshold, the UEcompares the number of the cells of the non-used frequencies havingradio strength higher than the threshold with the maximum number ofinter-frequency reported cells, included in the inter-frequency RACHreporting information in step 320.

If the number of the cells of the non-used frequencies having radiostrength higher than the threshold is not greater than the maximumnumber, the UE includes cell identification information of all thenon-used frequency cells satisfying the condition of step 316 in theRACH message in order of the highest radio strength in step 322. In thiscase, the cell identification information indicates inter-frequency cellIDs indicating the cell order in the inter-frequency cell info list forinter-frequency measurements, set in the SIB11/12, or indicates cell IDsincluded in the inter-frequency cell info list, and may not includefrequency information and primary CPICH information for thecorresponding cells. In this case, the measurement results for thecorresponding cells may be included in the RACH message. It is assumedherein for example, that the measurement results are not included in theRACH message.

However, if the number of the non-used frequency cells having radiostrength higher than the threshold is greater than the maximum number,the UE includes cell identification information for as many cells as themaximum number among the non-used frequency cells satisfying thecondition of step 316 in the RACH message in order of the highest radiostrength in step 324. In this case also, the cell identificationinformation, as described in step 322, indicates as many inter-frequencycell IDs or cell IDs as the maximum number, and the RACH message cancomprise measurement results for the corresponding cells.

In step 326, the RACH message established in steps 318, 324 or 310, isthen transmitted to an RNC over a RACH.

FIG. 4 is a flowchart illustrating an exemplary RNC operation ofreceiving a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention. A description of anRNC operation of transmitting inter-frequency RACH reporting informationcomprising an inter-frequency cell info list and an inter-frequency RACHreporting threshold on SIB11/12 will be omitted herein.

As illustrated in FIG. 4, an RNC receives a RACH message from a UE overa RACH in step 402, and extracts at least one inter-frequency cell ID(or cell ID) associated with the inter-frequency measurement from theRACH message in step 404. If the RACH message includes nointer-frequency cell ID (or cell ID), the RNC determines that the RACHmessage includes no inter-frequency measurement result information.

In step 406, the RNC acquires cell information corresponding to theextracted inter-frequency cell ID, i.e., frequency information andprimary CPICH information, referring to its own inter-frequency cellinfo list. In step 408, the RNC acquires inter-frequency measurementresults corresponding to the inter-frequency cell ID, referring to theRACH message. Specifically, in step 408, if there is no inter-frequencymeasurement result included in the RACH message, the RNC determines thata cell corresponding to the inter-frequency cell ID has radio strengthexceeding the threshold. Otherwise, if there is any inter-frequencymeasurement result included in the RACH message, the RNC analyzes andacquires the inter-frequency measurement results included in the RACHmessage.

The acquired inter-frequency measurement results are used for analyzinga communication environment of the UE and determining whether to performhandover.

FIG. 5 is a diagram illustrating an exemplary UE structure fortransmitting a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention.

As illustrated in FIG. 5, an exemplary UE comprises a SIB receiver 502,a SIB analyzer 504, a measurement report decision unit 506, ameasurement unit 508, and a measurement report unit 510. The SIBreceiver 502 receives SIB11/12 over a broadcast channel (BCH), and theSIB analyzer 504 acquires inter-frequency RACH reporting informationnecessary for inter-frequency measurement reporting from the SIB11/12.The inter-frequency RACH reporting information comprises aninter-frequency cell info list and an inter-frequency RACH reportingthreshold ‘Th’. The inter-frequency cell info list is delivered to themeasurement report unit 510, and the threshold ‘Th’ is delivered to themeasurement report decision unit 506.

The measurement unit 508 measures radio strength, i.e., Ec/No or RSCP,of a CPICH received from each of the cells of frequencies unused by theUE (i.e., the non-used frequencies). The measurement report decisionunit 506 compares the measurement results from the measurement unit 508with the threshold to determine whether to report the measurementresults. If the measurement result for at least one cell does not exceedthe threshold, the measurement report decision unit 506 determines notto perform the measurement reporting. However, if the measurement resultfor at least one cell exceeds the threshold, the measurement reportdecision unit 506 determines to perform the measurement reporting anddelivers the measurement result to the measurement report unit 510.

The measurement report unit 510 stores a cell ID mapping table generatedreferring to the inter-frequency cell info list, searches the cell IDmapping table for inter-frequency cell IDs corresponding to themeasurement results received from the measurement report decision unit506, especially to the measurement results of the cells having radiostrength exceeding the threshold, and generates measurement resultinformation including the searched inter-frequency cell IDs. Themeasurement result information comprises inter-frequency cell IDs, thenumber of which does not exceed the maximum number determined by theSIB11/12. In addition, the measurement result information can comprisecorresponding measurement results together with the inter-frequency cellID. The measurement result information is included in a RACH message andtransmitted to an RNC over a RACH.

FIG. 6 is a diagram illustrating an exemplary RNC structure forreceiving a RACH message for inter-frequency measurement reportingaccording to an embodiment of the present invention.

As illustrated in FIG. 6, an exemplary RNC comprises a SIB generator602, a SIB transmitter 604, a cell ID mapping unit 606, a RACH receiver608, and a measurement result analyzer 610. The SIB generator 602generates SIB11/12 including inter-frequency RACH reporting informationas the system information necessary for system access for each of aplurality of cells controlled. The generated SIB11/12 is transmitted bythe SIB transmitter 604 to the idle mode UEs and the connected mode UEslocated in the cells over a BCH. The inter-frequency RACH reportinginformation comprises an inter-frequency cell info list and aninter-frequency RACH reporting threshold. The inter-frequency cell infolist is shared between the SIB transmitter and the cell ID mapping unit606 and is used for generating a cell ID mapping table.

The RACH receiver 608 receives a RACH message from a UE over a RACH, anddetermines whether there is any inter-frequency measurement resultinformation included in the RACH message. If the inter-frequencymeasurement result information is included in the RACH message, theinter-frequency cell IDs included in the inter-frequency measurementresult information are provided to the cell ID mapping unit 606. If themeasurement results corresponding to the inter-frequency cell IDs areincluded in the inter-frequency measurement result information, themeasurement results are delivered to the measurement result analyzer610.

The cell ID mapping unit 606 acquires cell information corresponding toeach of the inter-frequency cell IDs included in the inter-frequencymeasurement result information, i.e. acquires frequency information andprimary CPICH information, referring to the cell ID mapping table, andprovides the acquired cell information to the measurement resultanalyzer 610. The measurement result analyzer 610 receives the cellinformation and determines whether measurement results corresponding tothe cell information have been provided from the RACH receiver 608. Ifthe measurement results corresponding to the cell information have notbeen provided, the measurement result analyzer 610 determines that thecell corresponding to the cell information has radio strength exceedingthe threshold notified through the SIB11/12. However, if the measurementresults corresponding to the cell information have been provided, themeasurement result analyzer 610 analyzes the measurement results for thecells corresponding to the cell information. The determined measurementresults are used for determining whether a communication environment ofthe UE is good and whether there is a need for handover.

A description has been made of an exemplary operation performed whenthere is no lur interface for the UE. If a serving RNC (SRNC) forcontrolling radio resources of the UE is different from a control RNC(CRNC), i.e., a drift RNC (DRNC), for controlling the cell where the UEis located, an lur interface between the SRNC and CRNC exists. In thiscase, the SRNC cannot acquire frequency information and primary CPICHinformation using only the inter-frequency cell IDs in the RACH message.This is because the cell where the UE is currently located is controllednot by the SRNC, but by the CRNC, and SIB11/12 including theinter-frequency cell info list referred to by the inter-frequency cellIDs is generated by the CRNC. If the SRNC is different from the CRNC inthis way, the SIB generator 602 and the SIB transmitter 604, referringto FIG. 6, belong to the CRNC that transmits a SIB to the cell where theUE is located, and the RACH receiver 608, the cell index (ID) mappingunit 606 and the measurement result analyzer 610 belong to the SRNC thatanalyzes the measurement results of the UE and controls hard handover.Then, the cell ID mapping unit 606, because it cannot share theinter-frequency cell info list with the SIB transmitter 604, acquirescell information corresponding to the inter-frequency cell ID throughthe following exemplary embodiments of the present invention.

Before a description of an exemplary operation performed when the lurinterface exists is given, a description will first be made of exemplarysignaling of the lur interface for enabling an operation of embodimentsof the present invention. In the following description, a Cell Updatemessage will be used as an example of the RACH message. An SRNC performscell update according to the Cell Update message, and determines whetherto perform hard handover of the UE according to measurement resultinformation included in the Cell Update message. If the SRNC determinesto perform hard handover, it sets up a dedicated channel to the UE andperforms hard handover according to the cell information acquired fromthe CRNC.

FIG. 7 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a first embodiment of thepresent invention. Herein, a UE is located in a cell controlled by aCRNC and communicates with a CN via an SRNC. Then, there is an lurinterface between the SRNC and the CRNC.

As illustrated in FIG. 7, in step 702, a UE sets, in a Cell Updatemessage, measurement results for the cells of the non-used frequencieshaving radio strength higher than a ‘threshold referred to SIB11/12’ asan inter-frequency cell IDs based on an inter-frequency cell info listin the SIB11/12, and transmits the Cell Update message to a CRNC. Instep 704, the CRNC forwards the Cell Update message to an SRNC alongwith an uplink (UL) signaling transfer message. At this moment, the CRNCconverts the inter-frequency cell IDs into cell information of the cellcorresponding to the inter-frequency cell IDs, i.e., frequencyinformation and primary CPICH information, and includes the cellinformation in the UL signaling transfer message. In step 706, the SRNCperforms cell update according to the Cell Update message included inthe UL signaling transfer message, and transmits a downlink (DL)signaling transfer message indicating cell update completion to theCRNC. In step 708, the CRNC transmits a Cell Update Confirm message tothe UE according to the DL signaling transfer message.

The SRNC determines to perform hard handover according to themeasurement results included in the UL signaling transfer message, andexchanges a Radio Link (RL) setup request message and an RL setupresponse message with the CRNC in steps 710 and 712, to allow the UE totransition to a Cell—Dedicated Channel (CELL_DCH) state. In step 714,the SRNC receives a Physical Channel reconfiguration complete messageindicating setup of a dedicated channel from the UE. Thereafter, in step716, the UE performs hard handover to a target cell corresponding to thefrequency information and primary CPICH information included in the ULsignaling transfer message according to an indication of the SRNC.

FIG. 8 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a second embodiment of thepresent invention. Herein, a UE is located in a cell controlled by aCRNC and communicates with a CN via an SRNC. In the followingdescription, a Cell Update message is used as an example of the RACHmessage.

As illustrated in FIG. 8, in step 802, a UE sets, in a Cell Updatemessage, measurement results for the cells of the non-used frequencieshaving radio strength higher than a ‘threshold referred to SIB11/12’ asan inter-frequency cell IDs based on an inter-frequency cell info listin the SIB11/12, and transmits the Cell Update message to a CRNC. Instep 804, the CRNC forwards the intact Cell Update message to an SRNCalong with a UL signaling transfer message. At this moment, the CRNCdoes not convert the inter-frequency cell IDs into cell information, andtransparently transmits the Cell Update message received from the UEalong with a UL signaling transfer message. The SRNC cannot analyze theinter-frequency cell IDs received through the UL signaling transfermessage because it does not have an inter-frequency cell info listassociated with the cell where the UE is located. In step 806, the SRNCperforms cell update according to the UL signaling transfer message, andtransmits a DL signaling transfer message indicating cell updatecompletion to the CRNC. In step 808, the CRNC transmits a Cell UpdateConfirm message to the UE according to the DL signaling transfermessage.

The SRNC determines to perform hard handover according to themeasurement results included in the UL signaling transfer message, andtransmits an RL setup request message for setup of a dedicated channelfor the UE to the CRNC in step 810, and receives an RL setup responsemessage from the CRNC in response to the RL setup request message instep 812. In step 814, the UE transmits a Physical Channelreconfiguration complete message indicating setup of a dedicated channelto the SRNC.

The CRNC includes, in the RL setup response message, cell ID mappingtable information for inter-frequency cell IDs included in the CellUpdate message set in step 802. The cell ID mapping table informationcomprises cell information such as the inter-frequency cell IDs andtheir associated frequency information and primary CPICH information.The SRNC allows the UE to perform hard handover to a target cell basedon the frequency information and primary CPICH information in step 816,using the cell ID mapping table information acquired through the RLsetup response message.

FIG. 9 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a third embodiment of thepresent invention. Herein, a UE is located in a cell controlled by aCRNC and communicates with a CN via an SRNC. In the followingdescription, a Cell Update message is used as an example of the RACHmessage.

As illustrated in FIG. 9, in step 902, a UE sets, in a Cell Updatemessage, measurement results for the cells of the non-used frequencieshaving radio strength higher than a ‘threshold referred to SIB11/12’ asan inter-frequency cell IDs based on an inter-frequency cell info listin the SIB11/12, and transmits the Cell Update message to a CRNC. Instep 904, the CRNC forwards the intact Cell Update message to an SRNCalong with a UL signaling transfer message. At this moment, the CRNCdoes not convert the inter-frequency cell IDs into cell information, andtransparently transmits the Cell Update message received from the UEalong with a UL signaling transfer message. The SRNC cannot analyze theinter-frequency cell IDs received through the UL signaling transfermessage because it does not have an inter-frequency cell info listassociated with the cell where the UE is located. In step 906, the SRNCperforms cell update according to the UL signaling transfer message, andtransmits a DL signaling transfer message indicating cell updatecompletion to the CRNC. In step 908, the CRNC transmits a Cell UpdateConfirm message to the UE according to the DL signaling transfermessage.

The SRNC determines to perform hard handover according to themeasurement results included in the UL signaling transfer message, andtransmits an RL setup request message for setup of a dedicated channelfor the UE to the CRNC in step 910. The CRNC transmits an RL setupresponse message to the SRNC in response to the RL setup request messagein step 912. In step 914, the UE transmits a Physical Channelreconfiguration complete message indicating setup of a dedicated channelto the SRNC.

The SRNC includes an inter-frequency cell ID of a target cell for hardhandover in the RL setup request message, and the CRNC receiving the RLsetup request message transmits cell information for the inter-frequencycell ID of the target cell, such as frequency information and primaryCPICH information, through the RL setup response message. The SRNCanalyzes the frequency information and the primary CPICH informationthrough the RL setup response message, and allows the UE to perform hardhandover to the target cell based on the frequency information andprimary CPICH information in step 916.

FIG. 10 is a message flow diagram for illustrating exemplary signalingbetween an SRNC and a CRNC according to a fourth embodiment of thepresent invention. Herein, a UE is located in a cell controlled by aCRNC. The CRNC controls the cell where the UE is currently located, andan SRNC controls radio resources of the UE and connects the UE to a CN.

As illustrated in FIG. 10, in step 1010, a UE transmits a Cell Updatemessage to a CRNC as an example of a RACH message. The Cell Updatemessage, as described with reference to FIG. 2, comprises measurementresults for the cells having radio strength exceeding a threshold amongneighboring cells of the non-used frequency bands, and the measurementresults have inter-frequency cell IDs indicating cell order in aninter-frequency cell info list given for inter-frequency measurement inSIB11/12, for the cells. The Cell Update message comprises‘Inter-frequency cell indication-SIB11’ and/or ‘Inter-frequency cellindication-SIB12’, which are indicators indicating an inter-frequencycell info list of which SIB out of SIB11 and SIB12 the inter-frequencycell IDs has referred to, and inter-frequency cell IDs based on theindicators. There can be a plurality of inter-frequency cell IDs in theCell Update message, and they are in order of the cells having thehighest radio strength.

In step 1015, the CRNC checks the Cell Update message. If the CellUpdate message includes measurement results for the non-used frequencycells, the CRNC transmits DL/UL UTRA Absolute Radio Frequency ChannelNumber (UARFCN) and Primary Common Pilot Channel (P-CPICH) informationindicating frequency information, and Primary Scrambling Codeinformation indicating primary CPICH information, as complete cellinformation corresponding to the inter-frequency cell IDs included inthe measurement results, in addition to a UL Signaling TransferIndication message, in step 1020. The UL Signaling Transfer Indicationmessage is used when the DRNC or the CRNC forwards messages transmittedover a CCCH to the SRNC. That is, the Cell Update message is forwardedto the SRNC along with the UL signaling transfer indication message, andno direct modification is made on the Cell Update message.

A difference between the fourth embodiment of FIG. 10 and the firstembodiment of FIG. 7 will now be described below. In the firstembodiment of FIG. 7, the CRNC directly modifies the RACH message. Thatis, the CRNC replaces inter-frequency cell IDs, which are RACHmeasurement results, included in the RACH message such as the CellUpdate message, with the corresponding cell information, and thenforwards the modified RACH message through the UL Signaling TransferIndication message. However, in the fourth embodiment of FIG. 10, theCRNC forwards the Cell Update message to the SRNC without modification.The CRNC includes cell information (DL UARFCN, UL UARFCN, and PrimaryScrambling Code) corresponding to the inter-frequency cell IDs, whichare RACH measurement results, included in the Cell Update message, as anadditional field, and transmits the Cell Update message to the SRNC.

Table 5 below shows, by way of example, a format of the UL SignalingTransfer Indication message according to the fourth embodiment of thepresent invention. In accordance with FIG. 2, cell information (DLUARFCN, UL UARFCN, and Primary Scrambling Code) corresponding to theinter-frequency cell IDs included in the RACH message (i.e., Cell Updatemessage) is included in an Inter-frequency Cell List of the UL SignalingTransfer Indication message. A description of information elements (IEs)unrelated to embodiments of the present invention will be omitted hereinfor clarity.

TABLE 5 Seman- As- tics signed IE/Group Pres- Descrip- Criti- Name enceRange tion Criticality cality Inter- 0 . . . <maxCellsMeas> GLOBALignore frequency Cell List  >DL M — UARFCN  >UL O — UARFCN  >Primary M —Scrambling Code

As described above, UARFCN indicates a frequency used in thecorresponding cell, and UL UARFCN and DL UARFCN indicate frequency bandsfor an uplink and a downlink, respectively. Primary Scrambling Codeindicates a scrambling code used for a P-CPICH of the correspondingcell, and can be used as a cell identifier. In addition, ‘maxCellsMeas’indicates the maximum number of non-used frequency cells measurable bythe UE, and as a result, it denotes the number of cells included in aninter-frequency cell info list included in the SIB11/12.

If the inter-frequency cell IDs for the several non-used frequency cellsare included in the RACH message as the inter-frequency measurementresults, several cell information can be included in the UL SignalingTransfer Indication message in order of the inter-frequency cell IDs.However, if no inter-frequency cell ID is included in the RACH messageas the inter-frequency measurement results, no cell information isincluded in the UL Signaling Transfer Indication message.

In FIG. 10, ‘Cell Info of the Measured Cells’ denoted in step 1020indicates cell information included in the UL Signaling TransferIndication message. In step 1030, a Cell Update Confirm message istransmitted from the SRNC to the UE via the CRNC as a response messageto the Cell Update message.

In step 1025, the SRNC checks whether it already sustains the entiremapping information of cell information per inter-frequency cell IDassociated with the cell (i.e., current cell) being controlled by theCRNC, based on the RACH measurement results of the RACH message includedin the UL Signaling Transfer Indication message. Herein, the ‘entiremapping information’ refers to a mapping list of the cell informationper inter-frequency cell ID for all cells included in theinter-frequency cell info list of the SIB11/12 transmitted from thecurrent cell. In the check process, the SRNC checks whether it firstreceives the UL Signaling Transfer Indication message including the cellinformation for the inter-frequency cell IDs from the CRNC.

If the SRNC was maintaining the entire mapping information of the cellinformation per inter-frequency cell ID associated with the current cellwhen it received the UL Signaling Transfer Indication message, the SRNCends the update procedure of the entire mapping information in step1030, and proceeds to a handover process of determining whether toperform hard handover for the UE. However, in step 1040, if the SRNC wasnot maintaining the entire mapping information of the cell informationper inter-frequency cell ID associated with the current cell when itreceived the UL Signaling Transfer Indication message, i.e., if the SRNCfirst receives the UL Signaling Transfer Indication message includingthe cell information for the inter-frequency cell IDs from the CRNC, theSRNC sends a request for the entire mapping information of the cellinformation per inter-frequency cell ID associated with the current cellto the CRNC through an Information Exchange Initiation Request messagein step 1045. The Information Exchange Initiation Request message iscommonly used by one RNC to send a request for start of informationexchange to another RNC. Table 6 below shows, by way of example, aformat of the Information Exchange Initiation Request message.

TABLE 6 Pre- Semantics Assigned IE/Group Name sence Range DescriptionCriticality Criticality Message Type M YES reject Transaction ID M —Information M YES reject Exchange ID CHOICE M YES reject InformationExchange Object Type Information Type M YES reject Information M YESreject Report Characteristics

The Information Exchange Initiation Request message comprises an‘Information Type’ IE, and the SRNC requests the entire mappinginformation of the cell information per inter-frequency cell IDassociated with a specific cell through the ‘Information Type’ IE. Forthis purpose, the ‘Information Type’ IE is set such that it indicates‘Inter-frequency Cell Information’. That is, in order to send a requestfor the entire mapping information of the cell information perinter-frequency cell ID associated with the specific cell to the CRNC,the SRNC sets an ‘Information Type Item’ IE of the ‘Information Type’ IEincluded in the Information Exchange Initiation Request message suchthat it indicates “Inter-frequency Cell Information”. The ‘Informationtype’ IE is used as an identifier indicating the requested information.Table 7 below shows, by way of example, an exemplary format of the‘Information Type’ IE included in the Information Exchange InitiationRequest message.

TABLE 7 IE/Group Pres- IE Type and Semantics Name ence Range ReferenceDescription Information M ENUMERATED For information Type Item (UTRANAccess exchange Point Position on the Iur-g with Altitude, interface,only the UTRAN Access Cell Capacity Point Position, Class is used. IPDLParameters, GPS Information, DGPS Corrections, GPS RX Pos, SFN-SFNMeasurement Reference Point Position, . . . , Cell Capacity Class, NACCRelated Data, MBMS Bearer Service Full Address, Inter-frequency CellInformation)

In addition, the SRNC can set an ‘Information Report Characteristics’ IEof the Information Exchange Initiation Request message such that itindicates “On Modification”. Each time the inter-frequency cell infolist included in the SIB11/12 of the specific cell is changed, the CRNCtransmits the entire mapping information of the cell information perinter-frequency cell ID based on the changed inter-frequency cell infolist to the SRNC through an Information Report message. In this way, theSRNC always maintains the latest entire mapping information of the cellinformation per inter-frequency cell ID associated with the specificcell. The ‘Information Report Characteristics’ IE indicates in which waythe information requested by the Information Exchange Initiation Requestmessage should be reported, and a format thereof is shown in Table 8below, by way of example.

TABLE 8 Semantics IE/Group Name Presence Range Description CHOICEInformation Report M Characteristics Type  >On Demand  >Periodic >>CHOICE Information M The frequency with  Report Periodicity Scalewhich the Node B shall send information reports.   >>>minute   >>>>Report M    Periodicity Value   >>>hour    >>>>Report M   Periodicity Value > On Modification  >>Information Threshold O

Returning to FIG. 10, in step 1050, the CRNC transmits an InformationExchange Initiation Response message to the SRNC in response to theInformation Exchange Initiation Request message. If the SRNC sent arequest for the entire mapping information of the cell information perinter-frequency cell ID associated with a specific cell to the CRNC instep 1045, the Information Exchange Initiation Response messagecomprises the information requested by the SRNC. Table 9 below shows, byway of example, an exemplary format of the Information ExchangeInitiation Response message.

TABLE 9 Semantics Assigned IE/Group Name Presence Range DescriptionCriticality Criticality Message Type M YES reject Transaction ID M —Information M YES ignore Exchange ID CHOICE Information O YES ignoreExchange Object Type  >Cell —  >>Requested Data M —  Value  >Additional—  Information Exchange  Object Types  >>MBMS Bearer —  Service  >>>MBMS Bearer 1 . . . <maxnoofMBMS> GLOBAL ignore   Service List  >>>>TMGI M —   >>>>Requested M —   Data Value Criticality DiagnosticsO YES ignore

The Information Exchange Initiation Response message includes in its‘Requested Data Value’ IE the entire mapping information of the cellinformation per inter-frequency cell ID associated with the cell,requested in step 1045. Table 10 below shows, by way of example, anexemplary format of the ‘Requested Data Value’ IE according to anembodiment of the present invention, and it includes an ‘Inter-frequencyCell Information’ IE.

TABLE 10 Semantics Assigned IE/Group Name Presence Range DescriptionCriticality Criticality UTRAN Access Point O — Position with Altitude IPDL Parameters O —  DGPS Corrections O —  GPS Navigation Model and O — Time Recovery  GPS Ionospheric Model O —  GPS UTC Model O —  GPSAlmanac O —  GPS Real-Time Integrity O —  GPS RX Pos O —  SFN-SFNMeasurement O —  Reference Point Position  Cell Capacity Class Value OYES ignore  NACC Related Data O YES ignore  MBMS Bearer Service Full OYES ignore  Address  Inter-frequency Cell O YES ignore  Information

Table 11 below shows, by way of example, a format of the‘Inter-frequency Cell Information’ IE.

TABLE 11 IE Type and IE/Group Name Presence Range Reference SemanticsDescription SIB11 0 . . . <maxCellSIB11>  >Inter-frequency M Integer(0 .. . 31) The order of the inter- cell id frequency cell in SIB11.  >DLUARFCN M UARFCN  >UL UARFCN O UARFCN If this IE is not present, thedefault duplex distance defined for the operating frequency band shallbe used [21]  >Primary M Scrambling Code SIB12 0 . . . <maxCellSIB12> >Inter-frequency M Integer(0 . . . 31) The order of the inter- cell idfrequency cell in SIB12.  >DL UARFCN M UARFCN  >UL UARFCN O UARFCN Ifthis IE is not present, the default duplex distance defined for theoperating frequency band shall be used [21]  >Primary M Scrambling CodeRange bound Explanation maxCellSIB11 Maximum number of inter-frequencycells broadcasted in SIB11. maxCellSIB12 Maximum number ofinter-frequency cells broadcasted in SIB12.

The ‘Inter-frequency Cell Information’ IE includes separate fields forSIB11/12. Each ‘inter-frequency cell id’ IE indicates a cell index ofthe inter-frequency cell info list provided for the inter-frequencymeasurements, and a ‘DL UARFCN’ IE and a ‘UL UARFCN’ IE each includeUL/DL frequency information for the non-used frequency cell indicated bythe inter-frequency cell index. A ‘Primary Scrambling Code’ IE indicatesa scrambling code used in a primary CPICH of the non-used frequency cellindicated by the inter-frequency cell index. The number of the“Inter-frequency Cell Information” IEs ranges from ‘0’ to ‘maxCellSIB11’or ‘maxCellSIB12’. The ‘maxCellSIB11’ indicates the maximum number ofthe non-used frequency cells included in the inter-frequency cell infolist provided for the inter-frequency measurements through the SIB11,and the ‘maxCellSIB12’ indicates the maximum number of the non-usedfrequency cells included in the inter-frequency cell info list providedfor the inter-frequency measurements through the SIB12.

As described above, if the ‘Information Report Characteristics’ IE ofthe Information Exchange Initiation Request message is set to “OnModification,” the CRNC transmits an Information Report message to theSRNC in step 1060, each time the inter-frequency cell info listassociated with the cell is modified in step 1055. The InformationReport message comprises the cell information per inter-frequency cellID updated according to the modified inter-frequency cell info list,i.e., the entire mapping information of the DL UARFCN, UL UARFCN andPrimary Scrambling Code.

FIGS. 11A and 11B are flowcharts illustrating an exemplary operation ofa CRNC according to the fourth embodiment of the present invention.

Referring to FIG. 11A, in step 1102, a CRNC receives a RACH messagehaving a ‘Measurement results for monitored cells on non-usedfrequencies’ IE included in a ‘Measured Result on RACH’ IE from a UElocated in a specific cell. In the following description, the specificcell where the UE is located will be referred to as a “current cell”.That is, step 1102 indicates reception of a RACH message includingmeasurement results for the non-used frequency cells. As describedabove, the RACH measurement results comprise inter-frequency cell IDs,i.e., an ‘inter-frequency cell id’ IEs, of the non-used frequency cellshaving radio strength exceeding a threshold. In step 1104, the CRNCfinds cell information corresponding to the ‘inter-frequency cell id’IEs of the RACH message, i.e., finds DL UARFCN, UL UARFCN and PrimaryScrambling Code. Because the RACH message includes ‘inter-frequency cellindication-SIB11/12’ which is an SIB11/12 use indicator indicating aninter-frequency cell IDs of which SIB out of SIB11/12 is used, the CRNCfinds cell information corresponding to each of the inter-frequency cellIDs using the SIB11/12 use indicator.

In step 1106, the CRNC includes cell information of the cellcorresponding to each of the inter-frequency cell IDs in a UL SignalingTransfer Indication message. If there is a need to transmit cellinformation for several cells, the CRNC includes the cell information inthe order of the inter-frequency cell IDs received through the RACHmessage. For example, if an ‘Inter-frequency cell id’ IE is set to ‘1’and ‘3’ in the RACH message, the CRNC first loads cell information forthe cell #‘1’ and next loads cell information for the cell #‘3’ in theUL Signaling Transfer Indication message. In step 1108, the CRNCtransmits the UL Signaling Transfer Indication message to an SRNC thatcontrols radio resources of the UE.

Referring to FIG. 11B, the CRNC receives an Information ExchangeInitiation Request message from the SRNC in step 1110, and checks instep 1112 whether the Information. Exchange Initiation Request messageneeds the entire mapping information of cell information perinter-frequency cell ID of an inter-frequency cell info list of SIB11/12transmitted from the current cell. As described above, this is possibleby checking whether an ‘Information Type’ IE of the Information ExchangeInitiation Request message is set to “Inter-frequency Cell Information”.If the ‘Information Type’ IE is set to the “Inter-frequency CellInformation”, the CRNC determines that the entire mapping information ofthe cell information per inter-frequency cell ID associated with thecurrent cell is needed.

If the result of step 1112 is ‘Yes’, the CRNC includes the entiremapping information of the cell information per inter-frequency cell IDassociated with the current cell in an Information Exchange InitiationResponse message responsive to the Information Exchange InitiationRequest message in step 1116. As described above, the entire mappinginformation is loaded on an ‘Inter-frequency Cell Information’ IE of a‘Requested Data Value’ IE included the Information Exchange InitiationResponse message. In step 1118, the Information Exchange InitiationResponse message is transmitted to the SRNC. However, if the result ofstep 1112 is ‘No’, the CRNC performs no specific operation for the RACHmeasurement reporting in step 1114.

After transmitting the Information Exchange Initiation Response messagein step 1118, the CRNC checks in step 1120 whether the ‘InformationReport Characteristics’ IE of the Information Exchange InitiationRequest message is set to “On Modification”. If the ‘Information ReportCharacteristics’ IE is set to “On Modification”, the CRNC transmits theentire mapping information of the cell information per inter-frequencycell ID updated by a changed inter-frequency cell info list each timethe inter-frequency cell info list of the current cell is changed, tothe SRNC through an Information Report message in step 1124. However, ifthe result of step 1120 is ‘No’, the CRNC performs a error handlingprocedure or does not transmit the entire mapping information of thecell information per inter-frequency cell ID updated for the changedlist to the SRNC in step 1122, even though the inter-frequency cell infolist of the current cell is changed.

FIG. 12 is a flowchart illustrating an exemplary operation of an SRNCaccording to the fourth embodiment of the present invention.

Referring to FIG. 12, in step 1202, an SRNC receives a messagecomprising cell information of a specific cell, such as DL UARFCN, ULUARFCN, and Primary Scrambling Code, from a CRNC accessed by a UE thatis under its control. In step 1204, the SRNC handles the receivedmessage. For example, if the received message is a UL Signaling TransferIndication message including a Cell Update message, the SRNC handles theCell Update message and transmits a Cell Update Confirm message to theUE via the CRNC. It will be assumed herein for example, that thereceived message is the UL Signaling Transfer Indication message.

In step 1206, the SRNC checks whether it already has the entire mappinginformation of the cell information per inter-frequency cell ID for thecurrent cell (for example, a cell from which the Cell Update message isgenerated) of the UE that generated the UL Signaling Transfer Indicationmessage. If the result of step 1206 is ‘Yes’, the SRNC takes no specificaction for RACH measurement reporting in step 1208.

However, if the result of step 1206 is ‘No’, the SRNC sets an‘Information Type’ IE of an Information Exchange Initiation Requestmessage to ‘Inter-frequency Cell Information’ in step 1210, to send arequest for the entire mapping information of the cell information perinter-frequency cell ID associated with the current cell to the CRNC. Instep 1212, the SRNC sets an ‘Information Report Characteristics’ IE ofthe Information Exchange Initiation Request message to “OnModification”. In step 1214, the SRNC transmits the Information ExchangeInitiation Request message including the ‘Information Type’ IE and the‘Information Report Characteristics’ IE to the CRNC.

Thereafter, upon receiving an Information Exchange Initiation Responsemessage including the entire mapping information of the cell informationper inter-frequency cell ID associated with the current cell in responseto the Information Exchange Initiation Request message, the SRNC storesthe entire mapping information and uses it for reception of the nextmeasurement result reporting. The SRNC updates the entire mappinginformation every time it receives an Information Report message.

As can be understood from the foregoing description, in performinginter-frequency measurement reporting on the non-used frequency cells inthe mobile communication system, the UE restricts unnecessarymeasurement reporting and minimizes information quality of the RACHmessage, thereby contributing to a reduction in uplink signalingoverhead.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A method for reporting an inter-frequencymeasurement result using a random access channel (RACH) message by aUser Equipment (UE) in a mobile communication system, the methodcomprising the steps of: receiving a system information block (SIB)comprising an inter-frequency cell information list for non-usedfrequency cells and a threshold from the system, for inter-frequencymeasurement reporting; measuring signal strengths of signals receivedfrom the non-used frequency cells and comparing the measured signalstrengths with the threshold; if there is any signal strength exceedingthe threshold, acquiring one or more inter-frequency cell identifiers(IDs) indicating one or more non-used frequency cells having the signalstrength exceeding the threshold referring to the inter-frequency cellinformation list; and transmitting the RACH message to the system, theRACH message including the one or more inter-frequency cell IDs asinter-frequency measurement result information, wherein theinter-frequency measurement result information comprises the one or moreinter-frequency cell IDs of non-used frequency cells having the signalstrength exceeding the threshold, the one or more inter-frequency cellIDs being ordered according to the signal strength of the non-usedfrequency cells.
 2. The method of claim 1, wherein the inter-frequencycell ID is configured to indicate an order of the non-used frequencycells included in the inter-frequency cell information list.
 3. Themethod of claim 1, wherein the number of the one or more non-usedfrequency cell IDs included in the inter-frequency measurement resultinformation does not exceed a maximum number indicated by the SIB. 4.The method of claim 1, wherein the RACH message further comprises anindicator for indicating the SIB referred to by the inter-frequency cellID.
 5. The method of claim 1, further comprising the step oftransmitting a RACH message without comprising the inter-frequencymeasurement result information therein, if there is no signal strengthexceeding the threshold.
 6. A user equipment (UE) apparatus forreporting an inter-frequency measurement result using a random accesschannel (RACH) message in a mobile communication system, the apparatuscomprising: a receiver for receiving, from a system, system informationblock (SIB) comprising an inter-frequency cell information list fornon-used frequency cells and a threshold from the system, forinter-frequency measurement reporting; a transmitter for transmittingthe RACH message to the system; and a controller for controllingoperations of measuring signal strengths of signals received from thenon-used frequency cells and comparing the measured signal strengthswith the threshold, if there is any signal strength exceeding thethreshold, acquiring one or more inter-frequency cell identifiers (IDs)indicating one or more non-used frequency cells having the signalstrength exceeding the threshold referring to the inter-frequency cellinformation list, and transmitting the RACH message to the system, theRACH message including the one or more inter-frequency cell IDs asinter-frequency measurement result information, wherein theinter-frequency measurement result information comprises the one or moreinter-frequency cell IDs of non-used frequency cells having the signalstrength exceeding the threshold, the one or more inter-frequency cellIDs being ordered according to the signal strength of the non-usedfrequency cells.
 7. The UE apparatus of claim 6, wherein theinter-frequency cell ID is configured to indicate an order of thenon-used frequency cells included in the inter-frequency cellinformation list.
 8. The UE apparatus of claim 6, wherein the number ofthe one or more non-used frequency cell IDs included in theinter-frequency measurement result information does not exceed a maximumnumber indicated by the SIB.
 9. The UE apparatus of claim 6, wherein theRACH message further comprises an indicator for indicating the SIBreferred to by the inter-frequency cell ID.
 10. The UE apparatus ofclaim 6, wherein the measurement report unit is configured to transmitthe RACH message without comprising the inter-frequency measurementresult information therein, if there is no signal strength exceeding thethreshold.